High tenacity or high load bearing nylon fibers and yarns and fabrics thereof

ABSTRACT

High strength or load bearing nylon fiber with break tenacity greater than 7.5 g/den and/or a tenacity at 10% elongation of greater than 4.0 g/den as well as yarns, fabrics and articles of manufacture thereof and methods for their production are provided.

FIELD OF INVENTION

The present disclosure relates to the preparation of improved nylonstaple fiber of desirably high strength as quantified by break tenacityand tenacity at 7% and 10% elongation. Such nylon staple fiber isproduced by preparing tows of relatively uniformly spun and quenchednylon filaments, drawing and annealing such tows in the presence ofsteam, and then cutting or otherwise converting the drawn and annealedtows into the desired high strength nylon staple fiber.

The nylon staple fiber so prepared can he blended with other fibers suchas cotton staple fiber to produce yarns which are also of desirably highstrength. Such yarns can then be made into fabrics and other articles ofmanufacture which can be advantageously lightweight, comfortable, lowercost, and durable and hence especially suitable for use in or as, forexample, military apparel such as combat uniforms or other rugged useapparel.

The present disclosure also relates to non-woven composites of hightenacity nylon fiber and cellulosic or recycled synthetic or naturalfiber technologies. End uses for such composites include, but are notlimited to, industrial (felts/backings/filtration/insulation), apparel(inclusive of liner fabrics), footwear, bag/pack hard gear, durable andsemi-durable (disposable or semi disposable) clothing or PPE, includingFR (chemically treated or in combination with inherent FR fibertechnologies), bio chemical, or other specialty protective wear.

BACKGROUND

Nylon has been manufactured and used commercially for a number of years.The first nylon fibers were of nylon 6,6, poly(hexamethylene adipamide),and nylon 6,6 fiber is still made and used commercially as the mainnylon fiber. Large quantities of other nylon fibers, especially nylon 6fiber prepared from caprolactam, are also made and used commercially.Nylon fiber is used in yarns for textile fabrics, and for otherpurposes. For textile fabrics, there are essentially two main yarncategories, namely continuous filament yarns and yarns made from staplefiber, i.e. cut fiber.

Nylon staple fiber has conventionally been made by melt-spinning nylonpolymer into filaments, collecting very large numbers of these filamentsinto a tow, subjecting the tow to a drawing operation and thenconverting the tow to staple fiber, e.g., in a staple cutter. The towusually contains many thousands of filaments and is generally of theorder of several hundred thousand (or more) in total denier. The drawingoperation involves conveying the tow between a set of feed rolls and aset of draw rolls (operating at a higher speed than the feed rolls) toincrease the orientation of nylon polymer in the filaments. Drawing isoften combined with an annealing operation to increase nyloncrystallinity in the tow filaments before the tow is converted intostaple fiber.

One of the advantages of nylon staple fibers is that they are readilyblended, particularly with natural fibers, such as cotton (oftenreferred to as short staple) and/or with other synthetic fibers, toachieve the advantages derivable from such blending. A particularlydesirable form of nylon staple fiber has been used for many years forblending with cotton, particularly to improve the durability andeconomics of the fabrics made from yarns comprising blends of cottonwith nylon. This is because such nylon staple fiber has a relativelyhigh load-bearing tenacity, as disclosed in Hebeler, U.S. Pat. Nos.3,044,250; 3,188,790; 3,321,448; and 3,459,845, the disclosures of whichare hereby entirely incorporated by reference. As explained by Hebeler,the load-bearing capacity of nylon staple fiber is conveniently measuredas the tenacity at 7% elongation (T7), and the T7 parameter has longbeen accepted as a standard measurement and is easily read on an Instronmachine.

The Hebeler process for preparing nylon staple fiber involves the nylonspinning, tow forming, drawing and converting operations hereinbeforedescribed. Improvements in the Hebeler process for preparing nylonstaple fiber have subsequently been made by modifying the nature of thetow drawing operation and by adding specific types of annealing (or hightemperature treatment) and subsequent cooling steps to the overallprocess. For example, Thompson in U.S. Pat. Nos. 5,093,195 and 5,011,645discloses nylon staple fiber preparation wherein nylon 6,6 polymer,having for example a formic acid relative viscosity (RV) of 55, is spuninto filaments which are then drawn, annealed, cooled and cut intostaple fiber having a tenacity, T, at break of about 6.8-6.9, a denierper filament of about 2.44, and a load-bearing capacity, T7, of fromabout 2.4 to 3.2. Such nylon staple fibers are further disclosed in theThompson patents as being blended with cotton and formed into yarns ofimproved yarn strength. (Both of these Thompson patents are incorporatedherein by reference in their entirety.)

Nylon staple fibers prepared in accordance with the Thompson technologyhave been blended into NYCO yarns (generally at a 50:50 nylon/cottonratio) with these yarns being used to prepare NYCO fabrics. Such NYCOfabrics, e.g., woven fabrics, find application in military combatuniforms and apparel. While such fabrics have generally provensatisfactory for military or other rugged apparel use, militaryauthorities, for example, are continually looking for improved fabricswhich may be lighter in weight, lower in cost and/or more comfortablebut still highly durable or even of improved durability.

SUMMARY OF THE INVENTION

The invention relates to creating a nylon staple fiber with extremelyhigh tenacity (both break tenacity and tenacity at low elongations). Theinvention involves the use of a steam to allow higher draw ratios versusnormal draw ratios used currently. The product is then annealed anddried under tension. The annealing/oven drying under tension helpsremove excess moisture gained during steam draw. The resulting fiberbreak tenacity has been increased from a 7.1 gram/den average to7.5-7.75 grams/denier range. Tenacity at 10% elongation has alsoincreased 10-20% higher versus standard product or previously describedimprovements. Fabrics made from this fiber are expected to exhibiteither higher strength in terms of grab and tear strength or comparablestrength but up to 1.0 oz. lighter in weight.

Accordingly, an aspect of the present invention relates to high strengthor load bearing nylon staple fiber with break tenacity greater than 7.5g/den and/or a tenacity at 10% elongation of greater than 4.0 g/den.

Another aspect of the present invention related to a yarn, at least aportion of which is spun from high strength or load bearing nylon staplefiber with break tenacity greater than 7.5 g/den and/or a tenacity at10% elongation of greater than 4.0 g/den.

In one embodiment, the yarns are made by blending these nylon staplefibers with at least one companion staple fiber.

In one embodiment, the yarns may be nylon/cotton (NYCO) yarns that canthen be woven into durable, and optionally lightweight, woven NYCOfabrics which can be especially suitable for military or other ruggedapparel use.

Another aspect of the present invention relates to a light weight fabricof less than 6.0 oz./yd² that meets or exceeds current military fabricsstrength and tear specifications established for fabrics that weigh >6.0oz./yd². The fabric is made up of a fiber blend at least a portion ofwhich comprises high strength or load bearing nylon fiber with breaktenacity greater than 7.5 g/den and a tenacity at 10% elongation ofgreater than 4.0 g/den.

Another aspect of the present invention relates to an article ofmanufacture, at least a portion of which comprises high strength or loadbearing nylon fiber with break tenacity greater than 7.5 g/den and/or atenacity at 10% elongation of greater than 4.0 g/den.

Another aspect of the present invention relates to non-woven fabriccomposites comprising high tenacity fiber and cellulosic or recycledsynthetic or natural fiber.

In one embodiment, the high tenacity fiber used in the non-woven fabriccomposite comprises load hearing nylon fiber with break tenacity greaterthan 7.5 g/den and/or a tenacity at 10% elongation of greater than 4.0g/den.

Yet another aspect of the present invention related to a method forproducing high strength or load bearing nylon fiber with break tenacitygreater than 7.5 g/den and/or a tenacity at 10% elongation of greaterthan 4.0 g/den. This method comprises the steps of melt-spinning nylonpolymer into filaments, uniformly quenching the filaments and forming atow from a multiplicity of these quenched filaments, subjecting the towto drawing in the presence of steam, annealing under tension, and thenconverting the resulting drawn and annealed tow into staple fiberssuitable for forming into, for example, spun yarn.

DETAILED DESCRIPTION OF THE INVENTION

Provided by this disclosure are high strength or load bearing nylonfiber with break tenacity greater than 7.5 g/den and/or a tenacity at10% elongation of greater than 4.0 g/den, yarns, fabrics and otherarticles of manufacture, at least a portion of which are prepared fromthese fibers, and methods for their production.

Also provided by this disclosure are non-woven fabric compositescomprising high tenacity fiber and cellulosic or recycled synthetic ornatural fiber.

As used herein, the terms “durable” and “durability” refer to thepropensity of a fabric so characterized to have suitably high grab andtear strength as well as resistance to abrasion for the intended end useof such fabric, and to retain such desirable properties for anappropriate length of time after fabric use has begun.

As used herein, the term blend or blended, in referring to a spun yarn,means a mixture of fibers of at least two types, wherein the mixture isformed in such a way that the individual fibers of each type of fiberare substantially completely intermixed with individual fibers of theother types to provide a substantially homogeneous mixture of fibers,having sufficient entanglement to maintain its integrity in furtherprocessing and use.

As used herein, cotton count refers to the yarn numbering system basedon a length of 840 yards, and wherein the count of the yarn is equal tothe number of 840-yard skeins required to weigh 1 pound.

All numerical values recited herein are understood to be modified by theterm “about”.

Some embodiments are based on the preparation of improved nylon staplefibers having certain specified characteristics and on the subsequentpreparation of yarns, and fabrics woven from such yarns, wherein theseimproved nylon staple fibers are blended with at least one other fiber.The other fibers may include cellulosics such as cotton, modifiedcellulosics such as FR treated cellulose, polyester, rayon, animalfibers such as wool, fire resistant (FR) polyester, FR nylon, FR rayon,FR treated cellulose, m-aramid, p-aramid, modacrylic, novoloid,melamine, polyvinyl chloride, antistatic fiber, PBO(1,4-benzenedicarboxylic acid, polymer with 4,6-diamino-1,3-benzenedioldihydrochloride), PBI (polybenzimidazole), and combinations thereof. Thenylon staple fibers of some embodiments can provide an increase instrength and/or abrasion resistance to yarns and fabrics. This isespecially true for combination with relatively weaker fibers such ascotton and wool.

The specific characteristics of the nylon staple fibers prepared andused herein include fiber denier, fiber tenacity and fiber load-bearingcapacity defined in terms of fiber tenacity at 7% and 10% elongation.

Realization of the desired nylon staple fiber material herein is basedon the use in staple fiber manufacture of nylon polymeric filaments andtows having certain selected properties and processed using certainselected processing operations and conditions. Specifically, theinventors herein have found that introduction of steam between the feedand draw module and/or tension during annealing significantly reducesdraw forces thus allowing the nylon supply to be drawn much furtherversus any dry draw process. In one embodiment of the present invention,steam is introduced into the normal nylon staple process by addition ofa steam chamber between the feed and draw modules as this allows theexcess water to be removed prior to annealing. Without being limited toany particular theory, it is believed that the steam chamber adds enoughheat/steam to reduce the draw force of the nylon and help localize thedraw to the steam chamber and not over or at the feed roll exit. Steamcan be controlled by pressure.

The nylon polymer itself which is used for the spinning of nylonfilaments of the present invention can be produced in conventionalmanner. Nylon polymer suitable for use in the process and filaments ofsome embodiments consists of synthetic melt spinnable or melt spunpolymer. Such nylon polymers can include polyamide homopolymers,copolymers, and mixtures thereof which are predominantly aliphatic,i.e., less than 85% of the amide-linkages of the polymer are attached totwo aromatic rings. Widely-used polyamide polymers such aspoly(hexamethylene adipamide) which is nylon 6,6 andpoly(.epsilon.-caproamide) which is nylon 6 and their copolymers andmixtures can be used in accordance with some embodiments. Otherpolyamide polymers which may be advantageously used are nylon 12, nylon4,6, nylon 6,10, nylon 6,12, nylon 12,12, and their copolymers andmixtures. Illustrative of polyamides and copolyamides which can beemployed in the process, fibers, yarns and fabrics of some embodimentsare those described in U.S. Pat. Nos. 5,077,124, 5,106,946, and5,139,729 (each to Cofer et al.) and the polyamide polymer mixturesdisclosed by Gutmann in Chemical Fibers International, pages 418-420,Volume 46, December 1996. These publications are all incorporated hereinby reference.

Nylon polymer used in the preparation of nylon staple fibers hasconventionally been prepared by reacting appropriate monomers,catalysts, antioxidants and other additives, such as plasticizers,delustrants, pigments, dyes, light stabilizers, heat stabilizers,antistatic agents for reducing static, additives for modifying dyeability, agents for modifying surface tension, etc. Polymerization hastypically been carried out in a continuous polymerizer or batchautoclave. The molten polymer produced thereby has then typically beenintroduced to a spin pack wherein it is forced through a suitablespinneret and formed into filaments which are quenched and then formedinto tows for ultimate processing into nylon staple fiber. As usedherein, spin pack is comprised of a pack lid at the top of the pack, aspinneret plate at the bottom of the pack and a polymer filter holdersandwiched between the former two components. The filter holder has acentral recess therein. The lid and the recess in the filter holdercooperate to define an enclosed pocket in which a polymer filter medium,such as sand, is received. There are provided channels interior to thepack to allow the flow of molten polymer, supplied by a pump or extruderto travel through the pack and ultimately through the spinneret plate.The spinneret plate has an array of small, precision bores extendingtherethrough which convey the polymer to the lower surface of the pack.The mouths of the bores form an array of orifices on the lower surfaceof the spinneret plate, which surface defines the top of the quenchzone. The polymer exiting these orifices is in the form of filamentswhich are then directed downwards through the quench zone.

The extent of polymerization carried out in the continuous polymerizeror batch autoclave can generally be quantified by means of a parameterknown as relative viscosity or RV. RV is the ratio of the viscosity of asolution of nylon polymer in a formic acid solvent to the viscosity ofthe formic acid solvent itself. RV is taken as an indirect indication ofnylon polymer molecular weight. For purposes herein, increasing nylonpolymer RV is considered synonymous with increasing nylon polymermolecular weight.

As nylon molecular weight increases, its processing becomes moredifficult due to the increasing viscosity of the nylon polymer.Accordingly, continuous polymerizers or batch autoclaves are typicallyoperated to provide nylon polymer for eventual processing into staplefiber wherein the nylon polymer has an RV value of about 60 or less.

It is known that for some purposes, provision of nylon polymer ofgreater molecular weight, i.e., nylon polymer having RV values ofgreater than 70-75 and up to 140 or even 190 and higher can beadvantageous. It is known, for example, that high RV nylon polymer ofthis type has improved resistance to flex abrasion and chemicaldegradation. Accordingly, such high RV nylon polymer is especiallysuitable for spinning into nylon staple fiber which can advantageouslybe used for the preparation of papermaking felts. Procedures andapparatus for making high RV nylon polymer and staple fiber therefromare disclosed in U.S. Pat. No. 5,236,652 to Kidder and in U.S. Pat. Nos.6,235,390; 6,605,694; 6,627,129 and 6,814,939 to Schwinn and West. Allof these patents are incorporated herein by reference in their entirety.

In accordance with some embodiments, it has been discovered that staplefibers prepared from nylon polymer having an RV value which is generallyconsistent with, or in some cases higher than, that generally obtainedvia polymerization in a continuous polymerizer or batch autoclave, whenprocessed in accordance with the spinning, quenching, feeding anddrawing in the presence of steam and annealing procedures describedherein, unexpectedly exhibit increased fiber break tenacity andincreased tenacity and 10% elongation as compared to standard product orpreviously described improvements. When such nylon staple fibers ofimproved tenacity are blended with one or more other fibers such ascotton staple fibers, textile yarns of improved strength as well aslower weight can be realized. Fabrics such as NYCO fabrics woven fromsuch yarns exhibit the advantages hereinbefore described with respect todurability, optional lighter weight, improved comfort and/or potentiallower cost.

In accordance with the staple fiber preparation process herein, nylonpolymer which is melt spun into tow-forming filaments through one ormore spin pack spinnerets and quenched will have an RV value rangingfrom 45 to 100, including from 55 to 100, from 46 to 65; from 50 to 60;and from 65 to 100. Nylon polymer of such RV characteristics can beprepared, for example, using a melt blending of polyamide concentrateprocedure such as the process disclosed in the aforementioned Kidder'652 patent. Kidder discloses certain embodiments in which the additiveincorporated into the polyamide concentrate is a catalyst for thepurpose of increasing the formic acid relative viscosity (RV). Higher RVnylon polymer available for melting and spinning, such as nylon havingan RV of from 65 to 100, can also be provided by means of a solid phasepolymerization (SPP) step wherein nylon polymer flakes or granules areconditioned to increase RV to the desired extent. Such solid phasepolymerization (SPP) procedures are well-known and disclosed in greaterdetail in the aforementioned Schwinn/West '390, '694, '129 and '939patents.

The nylon polymer material having the requisite RV characteristics asspecified herein are fed to a spin pack, for example via a twin screwmelter device. In the spin pack the nylon polymer is spun by extrusionthrough one or more spinnerets into a multiplicity of filaments. Forpurposes herein, the term “filament” is defined as a relativelyflexible, macroscopically homogeneous body having a high ratio of lengthto width across its cross-sectional area perpendicular to its length.The filament cross section can be any shape, but is typically circular.Herein, the term “fiber” can also be used interchangeably with the term“filament”.

Each individual spinneret position may contain from 100 to 1950filaments in an area as small as 9 inches by 7 inches (22.9cm.times.17.8 cm). Spin pack machines may contain from one to 96positions, each of which provides bundles of filaments which eventuallyget combined into a single tow band for drawing/downstream processingwith other tow bands.

After exiting the spinneret(s) of the spin pack, the molten filamentswhich have been extruded through each spinneret are typically passedthrough a quench zone wherein a variety of quenching conditions andconfigurations can be used to solidify the molten polymer filaments andrender them suitable for collection together into tows. Quenching ismost commonly carried out by passing a cooling gas, e.g., air, toward,onto, with, around and through the bundles of filaments being extrudedinto the quenching zone from each spinneret position within the spinpack.

One suitable quenching configuration is cross-flow quenching wherein acooling gas such as air is forced into the quenching zone in a directionwhich is substantially perpendicular to the direction that the extrudedfilaments are travelling through the quench zone, Cross-flow quenchingarrangements are described, among other quenching configurations, inU.S. Pat. Nos. 3,022,539; 3,070,839; 3,336,634; 5,824,248; 6,090,485,6,881,047 and 6,926,854, all of which patents are incorporated herein byreference.

In one embodiment of the staple fiber preparation process herein, theextruded nylon filaments used to eventually form the desired nylonstaple fibers are spun, quenched and formed into tows with bothpositional uniformity and uniformity of quenching conditions such asdescribed in published U.S. Patent Application Nos. 2011/0177737 and2011/0177738, teachings of which are herein incorporated by reference intheir entirety.

Quenched spun filaments can then be combined into one or more tows. Suchtows formed from filaments from one or more spinnerets are thensubjected to a two stage continuous operation wherein the tows are drawnand annealed in the presence of steam.

Drawing of the tows is generally carried out primarily in an initial orfirst drawing stage or zone wherein bands of tows are passed between aset of feed rolls and a set of draw rolls (operating at a higher speed)to increase the crystalline orientation of the filaments in the tow. Theextent to which tows are drawn can be quantified by specifying a drawratio which is the ratio of the higher peripheral speed of the drawrolls to the lower peripheral speed of the feed rolls. The effectivedraw ratio is calculated by multiplying the 1^(st) draw ratio and the2^(nd) draw ratio.

The first drawing stage or zone may include several sets of feed anddraw rolls as well as other tow guiding and tensioning rolls such assnubbing pins. Draw roll surfaces may be made of metal, e.g., chrome, orceramic. Ceramic draw roll surfaces have been found to be particularlyadvantageous in permitting use of the relatively higher draw ratiosspecified for use in connection with the staple fiber preparationprocess herein. Ceramic rolls improve roll life as well as provide asurface that is less prone to wrap. An article appearing theInternational Fiber Journal (International Fiber Journal, 17, 1,February 2002: “Textile and Bearing Technology for Separator Rolls”,Zeitz and el.) as well as U.S. Pat. No. 4,794,680, both incorporatedherein by reference, also disclose the use of ceramic rolls in toimprove roll life and reduce fiber adherence to roll surface.

While the greatest extent of drawing of the tows of filaments hereintakes place in the initial or first drawing stage or zone, someadditional drawing of the tows will generally also take place in asecond or annealing and drawing stage or zone hereinafter described. Thetotal amount of draw to which the filament tows herein are subjected canbe quantified by specifying a total effective draw ratio which takesinto account drawing that occurs in both a first initial drawing stageor zone and in a second zone or stage where annealing and someadditional drawing are conducted simultaneously.

In the process of some embodiments, the tows of nylon filaments aresubjected to a total effective draw ratio of from 2.3 to 5.0, includingfrom 3.0 to 4.0. In one embodiment wherein the denier per filament ofthe tows is generally smaller, a total effective draw ratio can rangefrom 3.12 to 3.40. In another embodiment, wherein the denier perfilament of the tows is generally larger, the total effective draw ratiocan range from 3.5 to 4.0.

In the process herein, most of the drawing of the tows, as notedhereinbefore, occurs in the first or initial drawing stage or zone. Inparticular, from 85% to 97.5%, including from 92% to 97%, of the totalamount of draw imparted to the tows will take place in the first orinitial drawing stage or zone. The drawing operation in the first orinitial stage will generally be carried out at whatever temperature thefilaments have when passed from the quench zone of the melt spinningoperation. Frequently, this first stage drawing temperature will rangefrom 80° C. to 125° C.

In the present invention, steam is introduced between feeding anddrawing to maximize draw of the nylon. In one embodiment, a steamchamber located between the feed and draw modules is used to allowhigher draw ratios versus normal draw ratios such as described herein.

From the first or initial drawing stage or zone, the partially drawntows are passed to a second annealing and drawing stage or zone whereinthe tows are simultaneously heated and further drawn. Heating of thetows to effect annealing serves to increase crystallinity of the nylonpolymer of the filaments. In this second annealing and drawing stage orzone, the filaments of the tows are subjected to an annealingtemperature of from 145° C. to 205° C., such as from 165° C. to 205° C.In one embodiment, the temperature of the tow in this annealing anddrawing stage may be achieved by contacting the tow with a steam-heatedmetal plate that is positioned between the first stage draw and thesecond stage drawing arid annealing operation. In the present invention,annealing/oven drying under tension helps remove excess moisture gainedduring steam draw.

After the annealing and drawing stage of the process herein, the drawnand annealed tows are cooled to a temperature of less than 80° C., suchas less than 75° C. Throughout the drawing, annealing and coolingoperations described herein, the tows are maintained under controlledtension and accordingly are not permitted to relax.

After drawing in the presence of steam and annealing/oven drying undertension, the multifilament tows are converted into staple fiber inconventional manner, for example using a staple cutter. Staple fiberformed from the tows will frequently range in length from 2 to 13 cm(0.79 to 5.12 inches). For example, staple fibers may range from 2 to 12cm (0.79 to 4.72 inches), from 2 to 12.7 cm (0.79 to 5.0 inches), orfrom 5 to 10 cm can be formed. The staple fiber herein can optionally becrimped.

The high tenacity nylon staple fibers formed in accordance with theprocess herein will generally be provided as a collection of fibers,e.g., as bales of fibers, having a denier per fiber of from 1.0 to 3.0.When staple fibers having a denier per fiber of from 1.6 to 1.8, arc tobe prepared, a total effective draw ratio of from 3.12 to 3.40, such asfrom 3.15 to 3.30, can be used in the process herein to provide staplefibers of the requisite load-bearing capacity. When staple fibers havinga denier per fiber of from 2.5 to 3.0 or 2.3 to 2.7 are to be prepared,a total effective draw ratio of from 3.5 to 4.0, or from 3.74 to 3.90,should be used in the process herein to provide staple fibers of therequisite load-bearing capacity.

Using this process and then annealing the fiber at 180° C. usingstandard annealing rolls produced a significantly higher tenacity fiberwith a tenacity greater than 7.5 g/den.

In one nonlimiting embodiment of the current invention a nylon staplefiber is disclosed with tenacity at break greater than 7.5 g/den. Inanother nonlimiting embodiment of the current invention nylon staplefiber is disclosed with tenacity at break greater than 7.8 g/den. Inanother nonlimiting embodiment of the current invention a nylon staplefiber is disclosed with tenacity at break of at least 8.0 g/den.

In one nonlimiting embodiment of the current invention a nylon staplefiber is disclosed a tenacity at 10% elongation of at least 4.0 g/den.

Fiber with properties above can be used at lower blend ratios or spuninto yarns using alternative spinning systems that significantly reducefabric manufacturing costs and still meet existing fabricsspecifications. A fiber that has very high tenacity (both break andtenacity at 7% or 10% elongation) and possibly stronger, lower cost orlighter weight fabrics that can be made from this fiber. This said fibercan be used to significantly reduce yarn spinning and finished fabriccosts by allowing the use of lower nylon blend levels and/or alternativespinning system while maintaining fabric properties. This offers valueto the down-steam customer versus competition. To achieve theseproperties in the fiber, a steam chamber is used help maximize draw ofthe nylon. The fiber tenacity obtained is higher than any produced onnormal staple equipment.

Having the ability to produce a significantly higher strength fiberversus completion is extremely advantageous. The higher strength nylonfiber allows yarns spinners and fabric weavers to reduce costs whilestill meeting strength requirements in the finished fabric/garment. Thishigher strength would put the competitive offering at a largedisadvantage in terms of cost. This cost difference potential could befrom $0.34 to over $1.00/lb. Example of lower cost yarns/fabrics includelower usage of nylon content in the spun yarn while still meeting yarnand fabric strength requirements and use of lower cost yarn spinningsystem (Vortex or OES) while still meeting fabric strength requirements.These lower cost alternatives could save over $1.00/fabric yard ifsuccessfully implemented. Having the ability to produce this higherstrength fiber gives significant advantages that the competition cannotmeet. Another possible advantage is allowing the production of lowerweight fabrics/garments while still meeting existing fabricspecifications. Adoption of the new fiber in any new fabricspecification such as lighter weight fabrics would prevent competitivefibers manufacturers from entering market.

The nylon staple fibers provided herein are especially useful forblending with other fibers for various types of textile applications.Blends can be made, for example, with the nylon staple fibers of someembodiments in combination with other synthetic fibers such as rayon orpolyester. Examples of blends of the nylon staple fibers herein includethose made with natural cellulosic fibers such as cotton, flax, hemp,jute and/or ramie. Suitable methods for intimately blending these fibersmay include: bulk, mechanical blending of the staple fibers prior tocarding; bulk mechanical blending of the staple fibers prior to andduring carding; or at least two passes of draw frame blending of thestaple fibers subsequent to carding and prior to yarn spinning.

In accordance with one embodiment, the high load-bearing capacity nylonstaple fibers herein may be blended with cotton staple fibers and spuninto textile yarn. Such yarns may be spun in conventional mariner usingcommonly known short and long staple spinning methods including ringspinning, air let or vortex spinning, open end spinning, or frictionspinning. When the yarn blend includes cotton, the resulting textileyarn will generally have a cotton fiber to nylon fiber weight ratio offrom 20:80 to 80:20, including from 40:60 to 60:40, and frequently acotton:nylon weight ratio of 50:50. It is well-known in the art thatnominal variation of the fiber content, e.g., 52:48 is also consideredto he a 50:50 blend. Textile yarns made with the high load-bearingcapacity nylon staple fibers herein will frequently exhibit LEA productvalues of at least 2800, such as at least 3000 at 50:50 NYCO content.Alternatively, such yarns may have a breaking tenacity of at least 17.5or 18 cN/tex, including at least 19 cN/tex, at 50:50 NYCO content.

In one embodiment, the textile yarns herein will be made from nylonstaple fibers having a denier per filament of from 1.6 to 1.8. Inanother embodiment, the textile yarns herein will be made from nylonstaple fibers having a denier per filament of from 2.5 to 3.0, includingfrom 2.3 to 2.7.

The nylon/cotton (NYCO) yarns of some embodiments can be used inconventional manner to prepare NYCO woven fabrics of especiallydesirable properties for use in military or other rugged use apparel.Thus such yarns may be woven into 2×1 or 3×1 twill NYCO fabrics. SpunNYCO yarns and 3×1 twill woven fabrics comprising such yarns are ingeneral described and exemplified in U.S. Pat. No. 4,920,000 to Green.This '000 patent is incorporated herein by reference.

NYCO woven fabrics, of course, comprise both warp and weft (fill) yarns.The woven fabrics of some embodiments are those which have the NYCOtextile yarns herein woven in an least one, and optionally both, ofthese directions. In one embodiment, fabrics herein of especiallydesirable durability and comfort will have yarns woven in the weft(fill) direction comprising nylon staple fibers herein which have adenier per filament of from 1.6 to 1.8 and will have yarns woven in thewarp direction comprising nylon staple fibers herein which have a denierper filament of from 2.3 to 3.0, including from 2.5 to 3.0, and from 2.3to 2.7 denier per filament.

The woven fabrics of some embodiments made using yarns which comprisethe high load bearing nylon staple fibers herein can use less of thenylon staple fibers than conventional NYCO fabrics while retaining manyof the desirable properties of such conventional NYCO fabrics. Thus,such fabrics can be made to be relatively lightweight and low cost whilestill desirably durable. Alternatively, such fabrics can be made usingequal or even greater amounts of the nylon staple fibers herein incomparison with nylon fiber content of conventional NYCO fabrics withsuch fabrics herein providing superior durability properties.

Lightweight fabrics such as NYCO fabrics of some embodiments may have afabric weight of less than 220 grams/m² (6.5 oz/yd²), including lessthan 200 grams/m² (6.0 oz/yd²), and less than 175 grams grams/m² (5.25oz/yd²). Suitable durable NYCO fabrics of the some embodiments will havea grab strength of 190 lbs or greater in the warp direction and 80 lbsor greater in the weft (fill) direction. Other durable fabrics have aTear Strength in “as received” fabric in warp direction of 11.0 lbf(poundfoot) or greater and fill direction of 9.0 lbf or greater.

The present invention also relates to non-woven fabric compositescomprising high tenacity fiber and cellulosic or recycled synthetic ornatural fiber. The inventors herein have found that inclusion of hightenacity fiber imparts additional tensile, tear, abrasion, washdurability and longevity to non woven substrates, inclusive of, but notlimited to, spunlace, airlaid, needlepunch and other carded non woventechnologies. In one embodiment, the high tenacity fiber used in thenon-woven fabric composite comprises load bearing nylon fiber with breaktenacity greater than 7.5 g/den and/or a tenacity at 10% elongation ofgreater than 4.0 g/den. As will be understood by the skilled artisanupon reading this disclosure, however, alternative high tenacity fiberssuch as, but not limited to, those described in published U.S. PatentApplication Nos. 2011/0177737 and 2011/0177738 can also be used.Additional nonlimiting examples of nylon staple fiber having arelatively high load-bearing tenacity which can be used in thesenon-woven composites are disclosed in U.S. Pat. Nos. 3,044,250;3,188,790; 3,321,448; 3,459,845; 5,093,195 and 5,011,645. The hightenacity fiber can be combined with various cellulosic or recycledsynthetic or natural fiber technologies including, but not limited to,recycled denim. End uses for the non-woven fabric composites include,but are not limited to, industrial(felts/backings/filtration/insulation), apparel (inclusive of linerfabrics), footwear, bag/pack hard gear, durable and semi-durable(disposable or semi disposable) clothing or PPE, including FR(chemically treated or in combination with inherent FR fibertechnologies), bio chemical, or other specialty protective wear.

Test Methods

When the various parameters, properties and characteristics for thepolymers, fibers, yarns and fabrics herein are specified, it isunderstood that such parameters, properties and characteristics can bedetermined using the following types of testing procedures andequipment:

Nylon Polymer Relative Viscosity

The formic acid RV of nylon materials used herein refers to the ratio ofsolution and solvent viscosities measured in a capillary viscometer at25° C. The solvent is formic acid containing 10% by weight of water. Thesolution is 8.4% by weight nylon polymer dissolved in the solvent. Thistest is based on ASTM Standard Test Method D 789. The formic acid RVsare determined on spun filaments, prior to or after drawing, and can bereferred to as spun fiber formic acid RVs.

Instron Measurements on Staple Fibers

All Instron measurements of staple fibers herein are made on singlestaple fibers, taking appropriate care with the clamping of the shortfiber, and making an average of measurements on at least 10 fibers.Generally, at least 3 sets of measurements (each for 10 fibers) areaveraged together to provide values for the parameters determined.

Filament Denier

Denier is the linear density of a filament expressed as weight in gramsof 9000 meters of filament. Denier can be measured on a Vibroscope fromTextechno of Munich, Germany. Denier times (10/9) is equal to decitex(dtex). Denier per filament can be determined gravimetrically inaccordance with ASTM Standard Test Method D 1577. A Favimat machinehaving a vibration based linear density measurement such as used in aVibroscope can also be used to determine DPF or denier per filament ofthe individual fiber and is comparable to ASTM D1577.

Tenacity at Break

Tenacity at break (T) is the maximum or breaking force of a filamentexpressed as force per unit cross-sectional area. The tenacity can bemeasured on an lnstron model 1130 available from Instron of Canton,Mass. and is reported as grams per denier (grams per dtex). Filamenttenacity at break (and elongation at break) can be measured according toASTM D 885.

Filament Tenacity at 7% and 10% Elongation

Filament tenacity at 7% elongation (T7) is the force applied to afilament to achieve 7% elongation divided by filament denier. T7 can bedetermined according to ASTM D 3822. Tenacity at 10% elongation can berun on a Favimat, which is comparable to ASTM D3822.

Yarn Strength

Strength of the spun nylon/cotton yarns herein can be quantified via aLea Product value or yarn breaking tenacity. Lea Product and skeinbreaking tenacity are conventional measures of the average strength of atextile yarn and can be determined in accordance with ASTM D 1578. LeaProduct values are reported in units of pounds force. Breaking tenacityis reported in units of cN/tex.

Fabric Weight

Fabric weight or basis weight of the woven fabrics herein can bedetermined by weighing fabric samples of known area and calculatingweight or basis weight in terms of grams/m² or oz/yd² in accordance withthe procedures of the standard test method of ASTM D 3776.

Fabric Crab Strength

Fabric grab strength can be measured in accordance with ASTM D 5034.Grab strength measurements are reported in pounds-force in both warp andfill directions.

Fabric Tear Strength—Elmendorf

Fabric tear strength can be measured in accordance with ASTM D 1424titled Standard Test Method for Tearing Strength of Fabrics byFalling-Pendulum Type (Elmendorf) Apparatus. Grab strength measurementsare reported in pounds-force in both warp and fill directions.

Fabric Abrasion Resistance—Taber

Fabric abrasion resistance can be determined as Taber abrasionresistance measured by ASTM D3884-01 titled Abrasion Resistance UsingRotary Platform Double Head Abrader. Results are reported in terms ofcycles to failure.

Fabric Abrasion Resistance—Flex

Fabric abrasion resistance can be determined as Flex abrasion resistancemeasured by ASTM D3885 titled Standard Test Method for AbrasionResistance of Textile Fabrics (Flexing and Abrasion Method). Results arereported in terms of cycles to failure.

The following section provides further illustration of the syntheticfiber and its characteristics as compared to fiber prepared by standardprocesses without steam draw assist. These working examples areillustrative only and are not intended to limit the scope of theinvention in any way.

EXAMPLES Example 1: Comparison of Standard T420 versus High StrengthT420

Properties of fiber produced in accordance with the steam draw assistprocess of the present invention were compared with fiber prepared by astandard process on a Favimat instrument after cutting and hailing.Results are shown in Table 1.

TABLE 1 Comparison of Standard T420 versus High Strength T420 (OerlikonAnalysis) Tenacity @ 10% Feed- Total Elongation Tenacity Elongation DrawDraw Process DPF (%) (g/den) (g/den) Ratio Ratio Standard 1.69 48   7.1 2.9  3.12 3.15 T420 Fiber High Strength 1.55 34   7.82 4.1  3.69 3.75T420 Fiber High Strength 1.59 35.7 8   4.54 3.97 4.05 T420 Fiber

1-17. (canceled)
 18. A method for producing high strength or loadbearing nylon fibers, said method comprising: (a) melt-spinning nylonpolymer into filaments; (b) uniformly quenching the filaments; (c)forming a tow from a multiplicity of the quenched filaments; (d)subjecting the tow to drawing in the presence of steam; (e) annealingthe drawn tow; and (f) converting the resulting drawn and annealed towinto staple fibers.
 19. The method of claim 18, wherein the nylonpolymer is nylon 6,6.
 20. The method of claim 18, wherein the drawing(d) comprises passing the tow from a set of feed rolls to a set of drawrolls while introducing steam to the tow.
 21. The method of claim 18,wherein the annealing (e) is performed under tension.
 22. The method ofclaim 18, wherein the nylon staple fiber has a break tenacity greaterthan 7.5 g/den.
 23. The method of claim 18, wherein the nylon staplefiber has a tenacity at 10% elongation of greater than 4.0 g/den.